They are good. They are quite high volume, so smooth riding, and they feel pretty "fast". The 25 is an excellent choice for rough surfaces.

On the downside, I rode them in the Alps recently and thought they felt a bit vague at higher speeds on descents.

I've used darn near everything in recent years in order to find "tire bliss". The bottom line is. It doesn't fully exist. Let me explain.
The michelins ride like a dream. Smooth, predictable. Even in the wet. However, anything resembling a sharp object will go right through. No matter how new they are. So,, then you try to find something more durable. With durability, comes compromise. Compromise will cost you that buttery smooth, yet super fast, feel.
I liked the responses for the Open Pave. This is a comfy (almost too much so) tire that you''ll be hard pressed to puncture under normal circumstances. However, you're going to go through more of these than just about everything else made. With the exception of maybe a veloflex or a challenge. They just aren't designed to last. And by not designed to last, I mean just that. They were never designed for a long lifespan. Smoothness, durability and speed come at the expense on longevity.
I had great luck last year with Vredesteins Tri comp Quattro. I got over 6,000k's on them and they're still quite rideable. Downsides being, Oversized alloy frame riders need not apply. They are some of the most unforgiving tires I've tried. Alot of people compare the ride to Conti's GP4000. Yeah, if you pumped the GP4000 up to 180psi and then filled them with cement. I'm sure then, they'd ride the same. I personally found the punishing ride worthwhile for the unreal durability and speed.
A great tire that most don't know about are the Gommitalia Calypsos. They can usually be found quite cheap and they're made the same way a Vittoria open corsa or a veloflex tire are made. The casing is made first, the rubber is glued on later. This makes for a much more compliant tire at high speed than a vulcanized tire such as a Maxxis or a Vredestein. They ride as smooth as the michelin. They wear quite well and have good puncture resistance. The sidewalls are the achiles heel of this tire. If you're on alot of gravel or really rough roads. Look elsewhere. The sidewalls cut too easily.
My current tire of choice are Vredestein Fortezza tri comps. Wicked fast tires with unreal cornering ability. Durability isn't as good as the Quattro, but the ride is alot smoother over rough surfaces.
For me, the Vreds are the cats ass. However, they aren't my recomendation for most people. The Conti GP4000 might be the best all around clincher ever made. It's not the fastest, or the toughest or the smoothest. Look at it like most three week races. The fastest sprinter never wins the overall. The best time trialist doesn't always win and the best climber doesn't always win. However, if a guy can time trial better than the climbers and climb better than the time trialers, he has a better chance of winning. The GP4000 isn't the fastest tire, but anything faster isn't durable. It's not the toughest tire, but anything tougher isn't fast enough. It's not the smoothest tire, but anything smoother again won't be as fast or as tough. I could recomend the GP4000 to 10 cyclist and have 9 very happy people. Try that with any other tire and you won't please half of them.
Abit of a hint. Most people are already aware of this. So this is just for the uneducated few. Latex tubes turn any tire into a much better tire. I've tried michelin and vittoria latex and can honestly say that the vittoria are head and shoulders above the michelin. Be aware though. They need to be properly inflated every ride whereas latex isn't air tight.

Besides the Vittoria latex tubes, I've found the Vredestein latex tubes to be just as supple and puncture proof, and about 20-25 grams lighter.

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Felt FC: viewtopic.php?f=10&t=116061

I haven't tried Vred. latex yet. It might be worth a look.

Vittoria Corsa Evo CX is my choice for bad roads. rocks, glass, potholes, you name it, they withstand it all. they are not that sharp as my 'regular' Michelin Pro2Race (yup!) and feel slightly slower. when i'm done with Pro2Race (got 3 more tires...) i'll probably stick with Vittorias, as Pro3 Race are rubbish and so are probably the 4s

GP4000S x23c - good vfm in my opinion

Let me join the chorus of recommendations for the Continental GP4000s in 700x25 size.

I now live in the LA area and regularly ride in the San Gabriel Mountains. My friends and I all rode Michelin Pro3's and then Pro4's, because they are very comfortable, and we all got serious punctures through the tire tread that required emergency boots to get back to civilization. The roads in the mountains have a lot of rockfall, and the sharp small stones that come down from the hillsides seem to go through the Michelins like a hot knife through butter. This is a shame, as i have been riding Michelins for years. In mid-summer we switched to the Conti GP4000s and have had much better luck (knock wood!).

My memory of Contis from many years ago was that they were rock hard, uncomfortable and very small for their stated size. The 4000s is not quite as comfortable as the Michelin, but it's comfortable enough. The tire now is generously sized in 700x25, and the tread compound seems to grip well. As for rolling resistance, I can only report that on descents I am recording times a bit faster than I did on the Michelins, so the rolling resistance can't be terrible.

Latest Tour magazine has a full test of clinchers and tubeless tyres.

Bottom line (from memory) was that the Conti GP4000 clincher is still best, with top or near-top marks on wet grip, rolling resistance, puncture resistance and everythign else they measure. Only the Conti TT clincher is faster, but this is only because it has no rubber on it, so one locked wheel and it's time for a new tyre. Michelins GP4 SC and GP4 Endurance also tested well, but they were a bit behind the Conti all round.

The test also showed that the latest Schwalbe tubeless tyre was pretty close to the GP4000 performance. But the Tour test included a 100g butyl tube in the clinchers, so if you put a latex tube or 50g supersonic tube inside the GP 4000 then it will be even better.

I've now been running the GP 4000 in 25 for two years and its been very reliable, reasonably durable, and with excellent ride & performance virtues. Just real happy with them. The Vittorias, Michelines, etc all seem to fall short in one area. The GP is well rounded without any significant shortcomings.

Make sure its the 4000S you get, the 4000 is completely different kettle of fish.

I had Ribino Slick pro's on the Cervelo when I got it, swapped em for the lighter, better grip in wet and much more durable 4000s' and havnt looked back. Stick in a set of conti supersonic 50g tubes for even more supple ride and just as puncture proof. Also tried 4 seasons, not bad but the 4000s beat them in grip and are just as durable and lighter

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Cervelo S3 2011. Blinged 6.718 Kg

Very well said!

Can't imagine why Tour tests with 100g tubes...

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formerly rruff...

1) Because most riders don't know better / don't have the skill to install a supersonic tube without puncturing it
2) Because otherwise there would be such a big performance gap that nobody would bother with tubeless, special rims, tyre milk, inflating with a compressor...

Got home and looked at Tour again. Yes I meant the 4000s in my earlier post. And the Schwalbe ZX clincher was also marginally better than the michelins in the tour test. Their conclusion was that any of the tyres they tested were good enough, and that the gap between best and worst is not that significant. So buy the cheapest or the one which matches your favourite socks.